Paradoxical effects of sublethal exposure to the naturally derived insecticide spinosad in the dengue vector mosquito,Aedes aegypti

BACKGROUND: Recent studies have indicated that spinosad, a mixture of two tetracyclic macrolide compounds produced during the fermentation of a soil actinomycete, may be suitable for controlling a number of medically important mosquito species, including the dengue vector, Aedes aegypti L. The authors determined the effects of a 1 h exposure to a 50% lethal concentration (LC₅₀) of spinosad in the larval stage on the wing length, longevity and reproductive capacity of the adult survivors. RESULTS: The LC₅₀ of spinosad for a wild‐caught population of Ae. aegypti from Chiapas, southern Mexico, was estimated to be 0.06 mg AI L^?1 in late third instars. Paradoxically, the female survivors of exposure to this concentration were significantly larger (as determined by wing length) laid more eggs, but were slightly less fertile than control females. This was probably due to elimination of the smaller and more susceptible fraction of mosquito larvae from the experimental population following spinosad treatment. Male survivors, in contrast, were significantly smaller than controls. No significant differences were detected in the adult longevity of treated and control insects of either sex. CONCLUSIONS: The increase in reproductive capacity of spinosad‐treated females did not compensate for mortality in the larval stage and would be unlikely to result in population increase in this mosquito under the conditions that were employed. Sustained‐release formulations would likely assist in minimizing the occurrence of sublethal concentrations of this naturally derived product in mosquito breeding sites. Copyright © 2008 Society of Chemical Industry     

异色瓢虫nAChRα6基因的敲除及其对杀虫剂敏感性的影响

为探索天敌昆虫异色瓢虫Harmonia axyridis基因功能研究的新技术及遗传改良的新途径,以其烟碱型乙酰胆碱受体α6亚基(nAChRα6)作为靶标基因,利用CRISPR/Cas9技术在异色瓢虫CAU-S品系中对其进行敲除,并测定多杀菌素、吡虫啉与阿维菌素对敲除纯合品系Haα6KO和野生型品系CAU-S的毒力,分析该基因的敲除是否影响异色瓢虫对这3种杀虫剂的敏感性。结果显示,通过CRISPR/Cas9介导的基因编辑及分子标记辅助筛选,成功获得异色瓢虫nAChRα6基因5号外显子缺失8 bp的敲除纯合品系Haα6KO。相对于野生型品系CAU-S,多杀菌素、吡虫啉与阿维菌素对敲除纯合品系Haα6KO的毒力指数分别为1.12、0.91和1.04,且3种杀虫剂对这2个品系的LC50的95%置信限无显著差异,表明异色瓢虫nAChRα6可能不是上述3种杀虫剂的作用靶标。本研究成功建立的CRISPR/Cas9介导的异色瓢虫基因编辑体系,可用于其基因功能研究及遗传改良。     

Monitoring of beet armyworm resistance to spinosad and methoxyfenozide in Mexico

BACKGROUND: Resistance to spinosad and methoxyfenozide has been studied in several insect pests, but there is a lack of information on Spodoptera exigua (Hübner) in Mexico. Therefore, evidence for the development of resistance in this pest to both compounds was examined. The effects of methoxyfenozide on reproductive parameters of S. exigua adults were also determined.RESULTS: Third instars from a field population were exposed for 24 h to the LC(50) of spinosad or methoxyfenozide for over six generations (G(2)-G(7)). No significant reduction in susceptibility to either compound was detected for up to five generations. In G(7), LC(50) values for insects exposed to spinosad and methoxyfenozide were respectively 2.75-fold and 1.25-fold greater than for G(1) larvae. Oral treatment with methoxyfenozide reduced the fecundity and fertility of G(7) adults, confirming sublethal effects on reproduction. Finally, five populations (Se-La Floriza, Se-Lazareto, Se-Bachigualato, Se-Los Agustinos and Se-Villa de Arista) of S. exigua were collected from fields in three states of Mexico for resistance monitoring to spinosad and methoxyfenozide. With the exception of Se-Villa de Arista, the other populations showed significant resistance to spinosad, with resistance ratios between 16- and 37-fold, compared with a susceptible laboratory colony. In contrast, only one population (Se-Lazareto) showed significant resistance to methoxyfenozide (13-fold).CONCLUSION: Resistance management programmes should be established, particularly in areas where S. exigua has developed resistance to spinosad. Copyright (c) 2008 Society of Chemical Industry.     

多杀菌素低剂量处理西花蓟马对药剂敏感性的影响

用低剂量多杀菌素继代处理西花蓟马(Frankliniella occidentalis)40多代后,测定了处理种群对其他5种不同类型杀虫剂的敏感性。结果表明,西花蓟马用多杀菌素LC25的浓度继代处理,对多杀菌素的敏感性逐渐下降。处理47代后,该种群的LC50是敏感种群的6.7倍,达到了低水平抗性。在第41代,当处理种群对多杀菌素的敏感性下降为敏感种群的5.19倍时,对阿维菌素和甲氨基阿维菌素苯甲酸盐的敏感性也下降,分别为敏感种群的2.68倍和2.92倍。     

小菜蛾阿维菌素和虫酰肼抗性品系对几种新型药剂的交互抗性研究

以敏感品系为对照,利用室内筛选获得的虫酰肼和阿维菌素高抗品系Teb-R和Aba-R,测定了小菜蛾对几种新型杀虫剂的交互抗性。结果发现:小菜蛾对虫酰肼产生高水平抗性后(抗性倍数185.5倍),对阿维菌素表现出中等水平交互抗性(41.0倍),对茚虫威(11.4倍)和溴虫腈(5.3倍)仅表现出低水平交互抗性,对多杀菌素(1.7倍)和氯虫苯甲酰胺(1.4倍)则没有表现出明显的交互抗性。用阿维菌素筛选Teb-R品系39代后获得阿维菌素高抗品系Aba-R(593.8倍),该品系对茚虫威(12.3倍)表现出中等水平交互抗性,对多杀菌素(7.9倍)表现出低水平交互抗性,对溴虫腈(2.7倍)和氯虫苯甲酰胺(0.9倍)的交互抗性不明显;同时该品系对虫酰肼的抗性也由阿维菌素筛选前的185.5倍下降到筛选后的28.0倍,也没有交互抗性。基于上述研究结果认为,使用虫酰肼防治小菜蛾出现抗性后,可以使用多杀菌素和氯虫苯甲酰胺进行替代防治,但不宜用阿维菌素、茚虫威和溴虫腈进行替代防治;利用阿维菌素防治小菜蛾产生抗性后,可以用溴虫腈、氯虫苯甲酰胺和虫酰肼进行替代防治,但不宜用多杀菌素和茚虫威。     

Feeding and attraction of non-target flies to spinosad-based fruit fly bait

A spinosad-based fruit fly bait, GF-120, has recently become a primary tool for area-wide suppression or eradication of pest tephritid fruit flies. The present study assessed the attraction and feeding of five non-target fly species to GF-120 in Hawaii. These non-target flies include three beneficial tephritid species [Eutreta xanthochaeta (Aldrich), Tetreuaresta obscuriventris (Loew), Ensina sonchi (L.)] introduced for weed biological control, an endemic Hawaiian tephritid [Trupanea dubautiae (Bryan)] (all Diptera: Tephritidae) and the cosmopolitan Drosophila melanogaster Meigen (Diptera: Drosophilidae). All five non-target fly species were susceptible to GF-120, as was the target pest Mediterranean fruit fly Ceratitis capitata (Wiedemann). Feeding on, or even brief tasting of, GF-120 killed all fly species within 2 h. When individual flies were provided with a choice of GF-120 or honey solution, there was no difference in the frequency of first food encounter by E. xanthochaeta, D. melanogaster or C. capitata. The other three non-target species approached honey more often than GF-120 in their first food encounter. Feeding times on GF-120 and honey were not significantly different for D. melanogaster and C. capitata, while the other four non-target species fed longer on honey than on GF-120. There was no significant difference in feeding time on honey versus GF-120 between males and females of each species. These results suggest that area-wide treatment using GF-120 for the purpose of eradication of pest fruit flies has potential negative impacts on these and other non-target fly species in Hawaii.     

Genetics and evidence for an esterase-associated mechanism of resistance to indoxacarb in a field population of diamondback moth (Lepidoptera: Plutellidae)

Bioassays (at generation G2) with a newly collected field population (designated CH3) of Plutella xylostella L. from farmers' fields in the Cameron Highlands, Malaysia, indicated resistance ratios of 813-, 79-, 171-, 498- and 1285-fold for indoxacarb, fipronil, spinosad, deltamethrin and Bacillus thuringiensis toxin Cry1Ac respectively compared with a laboratory susceptible population (Lab-UK). At G2 the field-derived population was divided into two subpopulations: one was selected (G2 to G7) with indoxacarb (indoxa-SEL), while the second was left unselected (UNSEL). A significant reduction in the resistance ratio for each compound was observed in UNSEL at G8. For indoxa-SEL, bioassays at G8 found that selection with indoxacarb gave a resistance ratio of 2594 compared with Lab-UK and of 90 compared with UNSEL. The toxicity of fipronil, spinosad and deltamethrin was not significantly different in indoxa-SEL at G8 compared with G2 but was significantly greater than UNSEL at G8. The toxicity of Cry1Ac was significantly reduced in indoxa-SEL at G8 compared with G2 but was also significantly greater than UNSEL at G8. This suggests that indoxacarb selection maintained resistance to these compounds in the indoxa-SEL population. Synergist studies indicated that resistance to indoxacarb in indoxa-SEL was esterase associated. Logit regression analysis of F1 reciprocal crosses between indoxa-SEL and Lab-UK indicated that resistance to indoxacarb was inherited as an autosomal, incompletely recessive (D(LC) = 0.35) trait. Tests of monogenic inheritance suggested that resistance to indoxacarb was controlled by a single locus.     

GlnA基因对刺糖多孢菌生长发育及多杀菌素合成的影响

谷氨酰胺合成酶（GS，glutamine synthetase）是由GlnA基因编码的生物体中最古老也是最广泛存在的酶，它参与许多生物体中的氮和碳代谢，是生物体氮代谢的关键酶之一，对微生物的生命活动起着重要作用。本文研究了GlnA基因对刺糖多孢菌Saccharopolyspora spinosa的生长发育及次级代谢产物合成的影响，从刺糖多孢菌基因组中克隆了glnA 基因的部分片段，将其与穿梭载体pOJ260连接，构建敲除载体pOJ260-glnA，通过接合转移将其导入刺糖多孢菌野生菌中，获得刺糖多孢菌敲除菌株S.spinosa-△glnA；同时，利用重叠延伸PCR将glnA基因置于红霉素强启动子P_ermE下，并将融合片段P_ermE-glnA与穿梭载体pOJ260进行酶切酶连，构建过量表达载体pOJ260-P_ermE-glnA，通过接合转移将其导入刺糖多孢菌中，获得了刺糖多孢菌过量表达菌株S.spinosa-glnA。表型分析发现，glnA基因的敲除对刺糖多孢菌的菌丝形态、孢子萌发等方面都有显著的抑制作用。HPLC检测分析发现，过量表达菌株中多杀菌素产量相比原始菌株提高到170%；该研究表明glnA基因对刺糖多孢菌的生长发育与多杀菌素的合成有一定的影响，为研究其在链霉菌次级代谢过程中的作用奠定了重要基础。     

橘小实蝇啤酒废酵母酶解蛋白中多杀菌素添加量的研究

为确定橘小实蝇(Bactrocera dorsalis)啤酒废酵母酶解蛋白中多杀菌素的添加量,室内测定了多杀菌素与啤酒废酵母酶解蛋白组配后对橘小实蝇的LC90、LT90及取食行为的影响.结果表明,多杀菌素对橘小实蝇雌、雄成虫在24 h内的LC90分别为5.461 5、7.308 5 mg/kg.2.5、6.3、16.0、40.0、100.0 mg/kg多杀菌素对橘小实蝇雌成虫的LT90分别为56.769 6、49.647 6、16.283 2、7.431 8、4.462 2 h,对雄成虫的LT90分别为57.388 8、52.165 2、17.615 2、7.562 8、4.834 5 h.40 mg/kg和100 mg/kg多杀菌素对6日龄和3日龄橘小实蝇雌雄成虫的取食量和吐出率均无显著影响.